In prior art, the manufacturing process of a central knife, a side knife and respective knife bearings of a mechanical balance for measuring large mass is simple, which can not achieve the hardness and toughness necessary for measuring a heavy weight. Moreover, in prior art, the load synchronization and the consistency between a main beam swing and an indication system of the mechanical balance are both poor, which makes the amount of the horizontal movements of a central knife system and a side knife system can not be reduced during a loading process, therefore the mechanical balance for measuring large mass can not acquire a high accuracy measurement in the progress of measuring the heavy weight.
According to the above reasons, in prior art, a measurement of a 500 kg weight with a repeatability of 0.05 g, a measurement of a 1000 kg weight with a repeatability of 0.5 g, and a measurement of a 2000 kg weight with a repeatability of 1 g can not be achieved.